|Concepts||two-component phase diagrams: limited solid solubility (Type 3)|
|Keywords||binary phase diagram, liquidus, solidus, metallurgy, lenticular, syncline, eutectic, solvus, alpha and beta structures, lamellar structure|
|Chemical Substances||solutions of ethylene glycol – water, chloride salt – water, cubic zirconia, aluminum-magnesium, lead-tin, aluminum-copper, aluminum-magnesium, iron-sulfur, ethanol-water|
|Applications||automobile antifreeze/coolant, deicing, manufacturing aluminum beverage cans, metallurgical failure analysis, aircraft metals, champagne|
Before starting this session, you should be familiar with:
After completing this session, you should be able to:
- Describe how a Type 3 binary phase diagram is a hybrid of Type 1 and Type 2 diagrams.
- Derive phase and composition information from a Type 3 binary phase diagram.
|[JS] 9.1, “The Phase Rule.”||Discussion of phase, component, and state; Gibbs phase rule; unary (one-component) phase diagram|
|[JS] 9.2, “The Phase Diagram.”||Binary phase diagrams; complete solid solutions; eutectic diagrams with no solid and limited solid solutions|
About this Video
This lecture begins with a quick review of Type 1 and Type 2 binary phase diagrams from the previous lecture.
This class introduces Type 3 binary phase diagrams, characterized by partial solubility of components A and B, a change of state, and freezing point depression of both components. It’s a hybrid of the Type 1 lenticular (lens) curve and Type 2 syncline curve. The eutectic is the lowest melting point on the diagram; it is a triple point where all three phases exist in equilibrium.
Prof. Sadoway presents some examples of Type 3 phase diagrams:
- ethylene glycol – water solution for automobile antifreeze/coolant;
- chloride salts – water mix for sidewalk and road deicing;
- cubic zirconia and how a jeweler can distinguish it from diamond;
- aluminum-magnesium alloy for easily-manufactured beverage cans;
- lead-tin mix for electronics soldering, with an extensive discussion of the alpha, beta, and lamellar microstructures that form while cooling;
- aluminum-copper for strength, e.g. airplane wings, constrasting with easily manufactured beverage cans;
- brief discussions of aluminum-magnesium and iron-sulfur solutions.
While considering these phase diagrams, he also describes the origins of the Fahrenheit temperature scale; and returns to how a material’s metallurgical microstructure is used for failure analysis (a topic introduced in Session 33).
Champagne manufacturing illustrates an ingenious use of solution chemistry as shown in binary phase diagrams.
The last few minutes of lecture are a preview of the final exam expectations and policies, some of Prof. Sadoway’s personal observations on the course, and a final champagne toast.
Congratulations! You’ve completed the final lecture.
For Further Study
Nicole Barbe Ponsardin (Madame Ponsardin Cliquot)
Other OCW and OER Content
|3.012 Fundamentals of Material Science||MIT OpenCourseWare||Undergraduate (second-year)||See Thermodynamics lectures 17-19 on multi-phase and binary phase diagrams, plus associated recitation and assignment content|
|Phase Diagrams and Solidification, Solid Solutions||DoITPoMS||Undergraduate|